1. Field of the Invention
The present invention relates to an optical semiconductor device including an optical semiconductor element and to a method of manufacturing the optical semiconductor device.
2. Description of the Related Art
Optical semiconductor devices are used in a broad range of fields as light sources for various devices including illuminating devices, display devices, and the like. This optical semiconductor device includes an optical semiconductor element, such as a light-emitting diode (LED), a first lead portion on which the optical semiconductor element is formed and bonded so as to establish electrical connection with the optical semiconductor element, and a second lead portion electrically connected to the optical semiconductor element on the first lead portion through a wire (see JP-A No. 2006-156538 (KOKAI) and JP-A No. 2006-66670 (KOKAI), for example). A voltage is applied to the first lead portion and the second lead portion and electric power is thereby applied to the optical semiconductor element.
A light-emitting layer is formed on a first principal surface of the optical semiconductor element, and a first electrode having a smaller size than the first principal surface is formed on the light-emitting layer. This first electrode is bonded to the first lead portion by use of a bonding member, such as solder, and the optical semiconductor element is formed on a mounting surface of the first lead portion. Meanwhile, a second principal surface located on the opposite side of the first principal surface is formed with a second electrode for connecting the wire. Here, the optical semiconductor element is sealed by mold resin.
In this optical semiconductor device, since the first lead portion is formed by press working and the like, the first lead portion has a low degree of flatness. Hence, in order to achieve bonding in which a bonding material, such as solder, is sufficiently filled in a space between the optical semiconductor element and the mounting surface of the first lead portion, it is necessary to thicken a bonding layer formed by the bonding member, or alternatively, to supply an auxiliary material, such as sheet solder, in addition to a bonding material, such as the solder.
However, the degree of flatness on the mounting surface of the first lead portion varies for each optical semiconductor device, and an amount of supply of the bonding member is set for the mounting surface having a low degree of flatness. Therefore, if the mounting surface has a high degree of flatness, the surplus bonding material runs off the space between the optical semiconductor element and the mounting surface of the first lead portion and climbs up along a sidewall of the optical semiconductor element. As the optical semiconductor is separated into an anode and a cathode according to the light-emitting layer, the contact of the bonding material with the sidewall of the optical semiconductor element causes a short-circuit failure.